In a known engine intake structure for a vehicle, an air inlet of an intake duct is defined by a depending wall depending from an upper wall of the intake duct and slanted rearward and an upright wall extending from a lower wall of the intake duct to be located behind the depending wall, such that the air inlet opens downward. See JP2013-130186A. In such an intake structure, the air introduced into the engine room of the vehicle through an upper grill passes through the air inlet as an upwardly directed flow along the depending wall. Therefore, moisture and other relatively heavy foreign matters that may be contained in the intake air are prevented from being introduced into the air duct.
According to this prior art, because the intake air is required to make sharp turns when flowing in the air inlet of the intake duct, flow resistance to the intake air is significant. Therefore, the intake inlet and other parts of the intake duct are required to have a large cross sectional area.